Until now in the field of sheet metal V-pulleys and sheet metal brake shoes, a manufacturing method such that a rotating slitting roller or a rotating cleaving roller is pressed against the outer peripheral portion of a circular metal material to split such portion into two parts is known (see Patent literatures 1 to 5). This method has advantages of excellent dimensional accuracy and reliability together with reduced manufacturing cost compared to a conventional method such as welding, press-forming, or casting, because the method can split accurately and easily a blank at a desired position in the thickness direction of the outer periphery thereof.
Further, Patent literatures 6 and 7 have disclosed a forming method in the manufacture of V-pulleys. In the disclosed method, one of two lugs (or formed portions of a guide), which are to be formed on the both sides of outer periphery of a cylindrical body bulging in the axial direction for prevention of V-belt slip-off, is formed by cleaving using a cylindrical-shaped cleaving punch.
Patent literature 8 has proposed a forming method in the manufacture of drum brakes. In the proposed method, the circumferential peripheral portion of a bottomed cylindrical metal body is cut by a cutting die in order to form a dust cover portion integrally with a flange portion and then the cut portion is drawn by a press die to form a cylindrical portion that works as the integrated dust cover.
Further, a method of end splitting for a workpiece of relatively soft material, different from a metal plate or a metal rod, has been disclosed in Patent literature 9. This method is to cut a divider strip of soft synthetic resin into longitudinal halves by pulling the divider strip with a cutter blade applied on the cross-section of the end thereof.
{Patent Literature 1}
                Japanese patent application laid-open No. 1986-129241{Patent Literature 2}        Japanese patent No. 3686903{Patent Literature 3}        Japanese patent application laid-open No. 1994-210361{Patent Literature 4}        Japanese patent No. 2520095{Patent Literature 5}        Japanese patent application laid-open No. 1996-267162{Patent Literature 6}        International publication No. WO 00/54905{Patent Literature 7}        Japanese patent application laid-open No. 1996-300082{Patent Literature 8}        Japanese patent application laid-open No. 2002-45940{Patent Literature 9}        Japanese utility model application laid-open No. 1988-78639        